Heat resistant thermoplastic articles including co-stabilizers

ABSTRACT

Disclosed is a molded or extruded thermoplastic article including a polyamide composition including (a) a polyamide resin having a melting point and/or glass transition; (b) one or more polyhydric alcohols having more than two hydroxyl groups and having a number average molecular weight (M n ) of less than 2000; (c) one or more co-stabilizer(s) (d) one or more reinforcement agents; wherein 4 mm test bars prepared from said polyamide composition, exposed at a test temperature at 170° C. for a test period of 500 hours have a retention of tensile strength, on average, of at least 50 percent, as compared with that of unexposed control of identical composition and shape.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of U.S. ProvisionalApplication No. 61/137,345, filed on 30 Jul. 2008 and currently pending.

FIELD OF THE INVENTION

The present invention relates to the field of molded and extrudedthermoplastic articles having improved long-term high temperature agingcharacteristics.

BACKGROUND OF INVENTION

High temperature resins based on polyamides possess desirable chemicalresistance, processability and heat resistance. This makes themparticularly well suited for demanding high performance automotive andelectrical/electronics applications. There is a current and generaldesire in the automotive field to have high temperature resistantstructures since temperatures higher than 150° C., even higher than 200°C., are often reached in underhood areas of automobiles. When plasticparts are exposed to such high temperatures for a prolonged period, suchas in automotive under-the-hood applications or inelectrical/electronics applications, the mechanical properties generallytend to decrease due to the thermo-oxidation of the polymer. Thisphenomenon is called heat aging.

In an attempt to improve heat aging characteristics, it has been theconventional practice to add heat stabilizers (also referred asantioxidants) to thermoplastic polyamide resins. Examples of such heatstabilizers include hindered phenol antioxidants, amine antioxidants andphosphorus-based antioxidants. For polyamide compositions, three typesof heat stabilizers are conventionally used to retain the mechanicalproperties of the composition upon exposure to high temperatures. One isthe use of phenolic antioxidants optionally combined with a phosphorusbased synergist as previously mentioned, the use of aromatic aminesoptionally combined with a phosphorus based synergist and the third oneis the use of copper salts and derivatives. Phenolic antioxidants areknown to improve the mechanical/physical properties of the thermoplasticcomposition up to an aging temperature of 120° C.

U.S. Pat. No. 5,965,652 discloses a thermally stable polyamide moldingcomposition containing colloidal copper formed in situ. However, thedisclosed compositions exhibit retention of impact strength only for aheat aging at 140° C.

GB patent 839,067 discloses a polyamide composition comprising a coppersalt and a halide of a strong organic base. However, the disclosedcompositions exhibit improved bending heat stability performance onlyfor a heat aging at 170° C.

Existing technologies lead not only to a poor improvement of long-termheat aging resistance, but also the improved heat aging characteristicsare insufficient for more demanding applications involving exposure tohigher temperatures such as for example in automotive under-the-hoodapplications and in electrical/electronics applications.

US 2006/0155034 and US 2008/0146718 patent publications disclosepolyamide compositions comprising a metal powder as thermal stabilizerwith a fibrous reinforcing agent. Disclosed compositions exhibitimproved mechanical properties such as tensile strength and elongationat break upon long-term heat aging at 215° C. However, such metalpowders are not only expensive but they are also highly unstable becausethey are prone to spontaneous combustion.

EP 1041109 discloses a polyamide composition comprising a polyamideresin, a polyhydric alcohol having a melting point of 150 to 280° C.,that has good fluidity and mechanical strength and is useful ininjection welding techniques.

Unfortunately, with the existing technologies, molded articles based onpolyamide or polyester compositions either suffer from an unacceptabledeterioration of their mechanical properties upon long-term hightemperature exposure or they are very expensive due to the use ofhigh-cost heat stabilizers.

There remains a need for low-cost polyamide compositions that aresuitable for manufacturing articles and that exhibit good mechanicalproperties after long-term high temperature exposure.

SUMMARY OF INVENTION

There is disclosed and claimed herein a molded or extruded thermoplasticarticle comprising a polyamide composition comprising

(a) a polyamide resin having a melting point and/or glass transition;

(b) 0.1 to 10 weight percent of one or more polyhydric alcohols havingmore than two hydroxyl groups and having a number average molecularweight (M_(n)) of less than 2000;

(c) 0.1 to 3 weight percent of one or more co-stabilizer(s) having a 10%weight loss temperature, as determined by thermogravimetric analysis, ofgreater than 30° C. below said melting point of said polyamide resin ifsaid melting point is present, or at least 250° C. if said melting pointis not present; selected from the group consisting of secondary arylamines and hindered amine light stabilizers, and mixtures thereof;

(d) 10 to 60 weight percent of one or more reinforcement agents; and

(e) 0 to 50 weight percent of a polymeric toughener comprising areactive functional group and/or a metal salt of a carboxylic acid;wherein all weight percentages are based on the total weight of thepolyamide composition; and wherein 4 mm test bars prepared from saidpolyamide composition, exposed at a test temperature at 170° C. for atest period of 500 hours, in an atmosphere of air, and tested accordingto ISO 527-2/1A, have a retention of tensile strength, on average, of atleast 50 percent, as compared with that of an unexposed control ofidentical composition and shape

Further disclosed is a molded or extruded thermoplastic article, asdisclosed above, wherein molded 4 mm test bars prepared from said polyamide composition, and exposed at a test temperature at 210° C. for atest period of 500 hours, in an atmosphere of air, and tested accordingto ISO 527-2/1A, have, on average, a retention of tensile strength of atleast 50 percent, as compared with that of an unexposed control ofidentical composition and shape.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the description, unless otherwise specified,“high-temperature” means a temperature at or higher than 170° C.,preferably at or higher than 210° C., and most preferably at or higherthan 230° C.

In the present invention, unless otherwise specified, “long-term” refersto an exposure period equal or longer than 500 hrs, preferably equal orlonger than 1000 hrs.

As used herein, the term “high heat stability”, as applied to thepolyamide composition disclosed herein or to an article made from thecomposition, refers to the retention of physical properties (forinstance, tensile strength) of 4 mm thick molded test bars consisting ofthe polyamide composition that are exposed to air oven aging (AOA)conditions at a test temperature at 170° C. for a test period of atleast 500 h, in an atmosphere of air, and then tested according to ISO527-2/1A method. The physical properties of the test bars are comparedto that of unexposed controls that have identical composition and shape,and are expressed in terms of “% retention”. In another preferredembodiment the test temperature is at 210° C., the test period is at 500hours and the exposed test bars have a % retention of tensile strengthof at least 70%. Herein “high heat stability” means that said moldedtest bars, on average, meet or exceed a retention for tensile strengthof 50% when exposed at a test temperature at 170° C. for a test periodof at least 500 h. Compositions exhibiting a higher retention ofphysical properties for a given exposure temperature and time periodhave better heat stability.

The terms “at 170° C.” and “at 210° C.” refer to the nominal temperatureof the environment to which the test bars are exposed; with theunderstanding that the actual temperature may vary by +/−2° C. from thenominal test temperature.

The term “(meth)acrylate” is meant to include acrylate esters andmethacrylate esters.

The polyamide resin used in the present invention has a melting pointand/or glass transition. Herein melting points and glass transitions areas determined with differential scanning calorimetry (DSC) at a scanrate of 10° C./min in the first heating scan, wherein the melting pointis taken at the maximum of the endothermic peak and the glasstransition, if evident, is considered the mid-point of the change inenthalpy.

Polyamides are condensation products of one or more dicarboxylic acidsand one or more diamines, and/or one or more aminocarboxylic acids,and/or ring-opening polymerization products of one or more cycliclactams. Suitable cyclic lactams are caprolactam and laurolactam.Polyamides may be fully aliphatic or semi-aromatic.

Fully aliphatic polyamides used in the resin composition of the presentinvention are formed from aliphatic and alicyclic monomers such asdiamines, dicarboxylic acids, lactams, aminocarboxylic acids, and theirreactive equivalents.

A suitable aminocarboxylic acid is 11-aminododecanoic acid. Suitablelactams are caprolactam and laurolactam. In the context of thisinvention, the term “fully aliphatic polyamide” also refers tocopolymers derived from two or more such monomers and blends of two ormore fully aliphatic polyamides. Linear, branched, and cyclic monomersmay be used.

Carboxylic acid monomers comprised in the fully aliphatic polyamidesinclude, but are not limited to aliphatic carboxylic acids, such as forexample adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaicacid (C9), decanedioic acid (C10), dodecanedioic acid (C12),tridecanedioic acid (C13), tetradecanedioic acid (C14), andpentadecanedioic acid (C15). Diamines can be chosen among diamineshaving four or more carbon atoms, including, but not limited totetramethylene diamine, hexamethylene diamine, octamethylene diamine,decamethylene diamine, dodecamethylene diamine, 2-methylpentamethylenediamine, 2-ethyltetramethylene diamine, 2-methyloctamethylenediamine;trimethylhexamethylenediamine, meta-xylylene diamine, and/or mixturesthereof.

The semi-aromatic polyamide is a homopolymer, a copolymer, a terpolymeror more advanced polymers formed from monomers containing aromaticgroups. One or more aromatic carboxylic acids may be terephthalate or amixture of terephthalate with one or more other carboxylic acids, suchas isophthalic acid, phthalic acid, 2-methyl terephthalic acid andnaphthalic acid. In addition, the one or more aromatic carboxylic acidsmay be mixed with one or more aliphatic dicarboxylic acids, as disclosedabove. Alternatively, an aromatic diamine such as meta-xylylene diamine(MXD) can be used to provide a semi-aromatic polyamide, an example ofwhich is MXD6, a homopolymer comprising MXD and adipic acid.

Preferred polyamides disclosed herein are homopolymers or copolymerswherein the term copolymer refers to polyamides that have two or moreamide and/or diamide molecular repeat units. The homopolymers andcopolymers are identified by their respective repeat units. Forcopolymers disclosed herein, the repeat units are listed in decreasingorder of mole % repeat units present in the copolymer. The followinglist exemplifies the abbreviations used to identify monomers and repeatunits in the homopolymer and copolymer polyamides (PA):

-   HMD hexamethylene diamine (or 6 when used in combination with a    diacid)-   T Terephthalic acid-   AA Adipic acid-   DMD Decamethylenediamine-   6 ε-Caprolactam-   DDA Decanedioic acid-   DDDA Dodecanedioic acid-   I Isophthalic acid-   MXD meta-xylylene diamine-   TMD 1,4-tetramethylene diamine-   4T polymer repeat unit formed from TMD and T-   6T polymer repeat unit formed from HMD and T-   DT polymer repeat unit formed from 2-MPMD and T-   MXD6 polymer repeat unit formed from MXD and AA-   66 polymer repeat unit formed from HMD and AA-   10T polymer repeat unit formed from DMD and T-   410 polymer repeat unit formed from TMD and DDA-   610 polymer repeat unit formed from 1,5-pentanediamine and DDA-   610 polymer repeat unit formed from HMD and DDA-   612 polymer repeat unit formed from HMD and DDDA-   6 polymer repeat unit formed from ε-caprolactam-   11 polymer repeat unit formed from 11-aminoundecanoic acid-   12 polymer repeat unit formed from 12-aminododecanoic acid

Note that in the art the term “6” when used alone designates a polymerrepeat unit formed from ε-caprolactam. Alternatively “6” when used incombination with a diacid such as T, for instance 6T, the “6” refers toHMD. In repeat units comprising a diamine and diacid, the diamine isdesignated first. Furthermore, when “6” is used in combination with adiamine, for instance 66, the first “6” refers to the diamine HMD, andthe second “6” refers to adipic acid. Likewise, repeat units derivedfrom other amino acids or lactams are designated as single numbersdesignating the number of carbon atoms.

In one embodiment the polyamide composition comprises a one or morepolyamides selected from the group consisting of

-   -   Group (I) Polyamides having said melting point of less than 210°        C., and comprising an aliphatic or semiaromatic polyamide        selected from the group poly(pentamethylene decanediamide)        (PA510), poly(pentamethylene dodecanediamide) (PA512),        poly(ε-caprolactam/hexamethylene hexanediamide) (PA6/66),        poly(ε-caprolactam/hexamethylene decanediamide) (PA6/610),        poly(ε-caprolactam/hexamethylene dodecanediamide) (PA6/612),        poly(hexamethylene tridecanediamide) (PA613), poly(hexamethylene        pentadecanediamide) (PA615), poly(ε-caprolactam/tetramethylene        terephthalamide) (PA6/4T), poly(ε-caprolactam/hexamethylene        terephthalamide) (PA6/6T), poly(ε-caprolactam/decamethylene        terephthalamide) (PA6/10T), poly(ε-caprolactam/dodecamethylene        terephthalamide) (PA6/12T), poly(hexamethylene        decanediamide/hexamethylene terephthalamide) (PA610/6T),        poly(hexamethylene dodecanediamide/hexamethylene        terephthalamide) (PA612/6T), poly(hexamethylene        tetradecanediamide/hexamethylene terephthalamide) (PA614/6T),        poly(ε-caprolactam/hexamethylene isophthalamide/hexamethylene        terephthalamide) (PA6/6I/6T), poly(ε-caprolactam/hexamethylene        hexanediamide/hexamethylene decanediamide) (PA6/6/610),        poly(ε-caprolactam/hexamethylene hexanediamide/hexamethylene        dodecanediamide) (PA6/66/612), poly(ε-caprolactam/hexamethylene        hexanediamide/hexamethylene decanediamide/hexamethylene        dodecanediamide) (PA6/66/610/612), poly(2-methylpentamethylene        hexanediamide/hexamethylene hexanediamide/hexamethylene        terephthamide) (PA D6/66//6T), poly(2-methylpentamethylene        hexanediamide/hexamethylene hexanediamide) (PA D6/66),        poly(decamethylene decanediamide) (PA1010), poly(decamethylene        dodecanediamide) (PA1012), poly(decamethylene decanediamide        decamethylene terephthalamide) (PA1010/10T) poly(decamethylene        decanediamide/dodecamethylene decanediamide decamethylene        terephthalamide/dodecamethylene terephthalamide        (PA1010/1210/10T/12T), poly(11-aminoundecanamide) (PA11),        poly(11-aminoundecanamide/tetramethylene terephthalamide)        (PA11/4T), poly(11-aminoundecanamide/hexamethylene        terephthalamide) (PA11/6T),        poly(11-aminoundecanamide/decamethylene terephthalamide)        (PA11/10T), poly(11-aminoundecanamide/dodecamethylene        terephthalamide) (PA11/12T), poly(12-aminododecanamide) (PA12),        poly(12-aminododecanamide/tetramethylene terephthalamide)        (PA12/4T), poly(12-aminododecanamide/hexamethylene        terephthalamide) (PA12/6T),        poly(12-aminododecanamide/decamethylene terephthalamide)        (PA12/10T) poly(dodecamethylene dodecanediamide) (PA1212), and        poly(dodecamethylene dodecanediamide/dodecamethylene        dodecanediamide/dodecamethylene terephthalamide)) (PA1212/12T);        Group (II) Polyamides having said melting point of at least 210°        C., and comprising an aliphatic polyamide selected from the        group consisting of poly(tetramethylene hexanediamide) (PA46),        poly(ε-caprolactam) (PA 6), poly(hexamethylene        hexanediamide)/(ε-caprolactam/) (PA 66/6) poly(hexamethylene        hexanediamide) (PA 66), poly(hexamethylene        hexanediamide/hexamethylene decanediamide) (PA66/610),        poly(hexamethylene hexanediamide/hexamethylene dodecanediamide)        (PA66/612), poly(hexamethylene hexanediamide/decamethylene        decanediamide) (PA66/1010), poly(hexamethylene decanediamide)        (PA610) poly(hexamethylene dodecanediamide) (PA612),        poly(hexamethylene tetradecanediamide) (PA614),        poly(hexamethylene hexadecanediamide) (PA616), and        poly(tetramethylene hexanediamide/2-methylpentamethylene        hexanediamide) (PA46/D6);    -   Group (III) Polyamides having said melting point of at least        210° C., and comprising        -   (aa) about 20 to about 35 mole percent semiaromatic repeat            units derived from monomers selected from one or more of the            group consisting of:            -   (i) aromatic dicarboxylic acids having 8 to 20 carbon                atoms and aliphatic diamines having 4 to 20 carbon                atoms; and        -   (bb) about 65 to about 80 mole percent aliphatic repeat            units derived from monomers selected from one or more of the            group consisting of:            -   (ii) an aliphatic dicarboxylic acid having 6 to 20                carbon atoms and said aliphatic diamine having 4 to 20                carbon atoms; and            -   (iii) a lactam and/or aminocarboxylic acid having 4 to                20 carbon atoms;    -   Group (IV) Polyamides comprising        -   (cc) about 50 to about 95 mole percent semiaromatic repeat            units derived from monomers selected from one or more of the            group consisting of:            -   (i) aromatic dicarboxylic acids having 8 to 20 carbon                atoms and aliphatic diamines having 4 to 20 carbon                atoms; and        -   (dd) about 5 to about 50 mole percent aliphatic repeat units            derived from monomers selected from one or more of the group            consisting of:            -   (ii) an aliphatic dicarboxylic acid having 6 to 20                carbon atoms and said aliphatic diamine having 4 to 20                carbon atoms; and            -   (iii) a lactam and/or aminocarboxylic acid having 4 to                20 carbon atoms;    -   Group (V) Polyamides having said melting point of at least 260°        C., and comprising        -   (ee) greater than 95 mole percent semiaromatic repeat units            derived from monomers selected from one or more of the group            consisting of            -   (i) aromatic dicarboxylic acids having 8 to 20 carbon                atoms and aliphatic diamines having 4 to 20 carbon                atoms; and        -   (ff) less than 5 mole percent aliphatic repeat units derived            from monomers selected from one or more of the group            consisting of:            -   (ii) an aliphatic dicarboxylic acid having 6 to 20                carbon atoms and said aliphatic diamine having 4 to 20                carbon atoms;            -   (iii) a lactam and/or aminocarboxylic acid having 4 to                20 carbon atoms; and    -   Group (VI) Polyamides having no melting point selected from the        group consisting of poly(hexamethylene        isophthalamide/hexamethylene terephthalamide) (6I/6T) and        poly(hexamethylene isophthalamide/hexamethylene        terephthalamide/hexamethylene hexanediamide) (6I/6T-66).

Group (I) Polyamides may have semiaromatic repeat units to the extentthat the melting point is less than 210° C. and generally thesemiaromatic polyamides of the group have less than 40 mole percentsemiaromatic repeat units. Semiaromatic repeat units are defined asthose derived from monomers selected from one or more of the groupconsisting of: aromatic dicarboxylic acids having 8 to 20 carbon atomsand aliphatic diamines having 4 to 20 carbon atoms.

Another embodiment is a molded or extruded thermoplastic article whereinsaid polyamide resin is selected from Group (III) Polyamides selectedfrom the group consisting of poly(tetramethylenehexanediamide/tetramethylene terephthalamide) (PA46/4T),poly(tetramethylene hexanediamide/hexamethylene terephthalamide)(PA46/6T), poly(tetramethylene hexanediamide/2-methylpentamethylenehexanediamide/decamethylene terephthalamide) PA46/D6/10T)poly(hexamethylene hexanediamide/hexamethylene terephthalamide)(PA66/6T), poly(hexamethylene hexanediamide/hexamethyleneisophthalamide/hexamethylene terephthalamide PA66/6I/6T, andpoly(hexamethylene hexanediamide/2-methylpentamethylenehexanediamide/hexamethylene terephthalamide (PA66/D6/6T); and a mostpreferred Group (III) polyamide is PA66/6T.

Another embodiment is a molded or extruded thermoplastic article whereinsaid polyamide resin is selected from Group (IV) Polyamides selectedfrom the group consisting of poly(tetramethyleneterephthalamide/hexamethylene hexanediamide) (PA4T/66),poly(tetramethylene terephthalamide/2-caprolactam) (PA4T/6),poly(tetramethylene terephthalamide/hexamethylene dodecanediamide)(PA4T/612), poly(tetramethylene terephthalamide/2-methylpentamethylenehexanediamide/hexamethylene hexanediamide) (PA4T/D6/66),poly(hexaamethylene terephthalamide/2-methylpentamethyleneterephthalamide/hexamethylene hexanediamide) (PA6T/DT/66),poly(hexamethylene terephthalamide/hexamethylene hexanediamide) PA6T/66,poly(hexaamethylene terephthalamide/hexamethylene decanediamide)(PA6T/610), poly(hexamethylene terephthalamide/hexamethylenetetradecanediamide) (PA6T/614), poly(nonamethyleneterephthalamide/nonamethylene decanediamide) (PA9T/910),poly(nonamethylene terephthalamide/nonamethylene dodecanediamide)(PA9T/912), poly(nonamethylene terephthalamide/11-aminoundecanamide)(PA9T/11), poly(nonamethylene terephthalamide/12-aminododecanamide)(PA9T/12), poly(decamethylene terephthalamide/11-aminoundecanamide) (PA10T/11), poly(decamethylene terephthalamide/12-aminododecanamide)(PA10T/12) poly(decamethylene terephthalamide/decamethylenedecanediamide) (PA10T/1010), poly(decamethyleneterephthalamide/decamethylene dodecanediamide) (PA10T/1012),poly(decamethylene terephthalamide/tetramethylene hexanediamide)(PA10T/46), poly(decamethylene terephthalamide/ε-caprolactam) (PA10T/6),poly(decamethylene terephthalamide/hexamethylene hexanediamide)(PA10T/66), poly(dodecamethylene terephthalamide/dodecamethylenedodecanediamide) (PA12T/1212), poly(dodecamethyleneterephthalamide/ε-caprolactam) (PA12T/6), and poly(dodecamethyleneterephthalamide/hexamethylene hexanediamide) (PA12T/66); and a mostpreferred Group (V) polyamide is PA6T/66.

Another embodiment is a molded or extruded thermoplastic article whereinsaid polyamide resin is selected from Group (V) Polyamides selected fromthe group consisting of poly(tetramethyleneterephthalamide/2-methylpentamethylene terephthalamide) PA4T/DT,poly(tetramethylene terephthalamide/hexamethylene terephthalamide)PA4T/6T, poly(tetramethylene terephthalamide/decamethyleneterephthalamide) PA4T/10T, poly(tetramethyleneterephthalamide/dodecamethylene terephthalamide)PA4T/12T,poly(tetramethylene terephthalamide/2-methylpentamethyleneterephthalamide/hexamethylene terephthalamide) (PA4T/DT/6T),poly(tetramethylene terephthalamide/hexamethyleneterephthalamide/2-methylpentamethylene terephthalamide) (PA4T/6T/DT),poly(hexamethylene terephthalamide/2-methylpentamethyleneterephthalamide) (PA6T/DT), poly(hexamethylenehexanediamide/hexamethylene isophthalamide) (PA6T/6I),poly(hexamethylene terephthalamide/decamethylene terephthalamide)PA6T/10T, poly(hexamethylene terephthalamide/dodecamethyleneterephthalamide) (PA6T/2T), poly(hexamethyleneterephthalamide/2-methylpentamethyleneterephthalamide/poly(decamethylene terephthalamide) (PA6T/DT/10T),poly(hexamethylene terephthalamide/decamethyleneterephthalamide/dodecamethylene terephthalamide) (PA6T/10T/12T)poly(decamethylene terephthalamide) (PA10T), poly(decamethyleneterephthalamide/tetramethylene terephthalamide) (PA10T/4T),poly(decamethylene terephthalamide/2-methylpentamethyleneterephthalamide) (PA10T/DT), poly(decamethyleneterephthalamide/dodecamethylene terephthalamide) (PA10T/12 T),poly(decamethylene terephthalamide/2-methylpentamethyleneterephthalamide/(decamethylene terephthalamide) (PA10T/DT/12T).poly(dodecamethylene terephthalamide) (PA12T), poly(dodecamethyleneterephthalamide)/tetramethylene terephthalamide) (PA12T/4T),poly(dodecamethylene terephthalamide)/hexamethylene terephthalamide)PA12T/6T, poly(dodecamethylene terephthalamide)/decamethyleneterephthalamide) (PA12T/10T), and poly(dodecamethyleneterephthalamide)/2-methylpentamethylene terephthalamide) (PA12T/DT); anda most preferred Group (V) polyamide is PA6T/DT.

In various embodiments the polyamide is a Group (I) Polyamide, Group(II) Polyamide, Group (III) Polyamide, Group (IV) Polyamide, Group (V)Polyamide or Group (VI) Polyamide, respectively.

The polyamides may also be blends of two or more polyamides. Preferredblends include those selected from the group consisting of Group (I) andGroup (II) Polyamides; Group (I) and Group (III) Polyamide, Group (I)and Group (VI) Polyamides, Group (I) and Group (III) Polyamides, Group(II) and Group (IV) Polyamides, Group (II) and Group (V) Polyamides,Group (II) and Group (VI) Polyamides, Group (III) and Group (VI)Polyamides, and Group (IV) and Group (V) Polyamides.

A preferred blend includes Group (II) and Group (V) Polyamides, and aspecific preferred blend includes poly(hexamethylene hexanediamide) (PA66) and poly(hexamethylene terephthalamide/2-methylpentamethyleneterephthalamide) (PA 6T/DT).

Another preferred blend includes Group (II) and Group (III) Polyamidesand a specific preferred blend includes poly(ε-caprolactam) (PA6) andpoly(hexamethylene hexanediamide/hexamethylene terephthalamide(PA66/6T).

Another embodiment is a molded or extruded thermoplastic articlecomprising a thermoplastic polyamide composition as disclosed above,wherein molded 4 mm test bars prepared from said polyamide composition,and exposed at a test temperature at 210° C. for a test period of 500hours, in an atmosphere of air, and tested according to ISO 527-2/1A,have, on average, a retention of tensile strength of at least 50percent, as compared with that of an unexposed control of identicalcomposition and shape. Thermoplastic polyamide compositions meetingthese test requirements are referred to as “meeting the requirements ofAOA 210° C./500 hours testing.”

The thermoplastic polyamide compositions meeting the requirements of AOA210° C./500 hours testing comprise one or more polyamide resins whereinsaid polyamide resin comprises a one or more polyamides independentlyselected from the groups consisting of Group (II) polyamides, Group(III) polyamides, Group (IV) polyamides, Group (V) polyamides and Group(VI) polyamides, as disclosed above.

In various embodiments thermoplastic polyamide compositions meeting therequirements of AOA 210° C./500 hours are Group (II) polyamides, Group(III) Polyamides, Group (IV) Polyamides, Group (V) Polyamides and Group(VI) Polyamides, respectively.

A further preferred embodiment is the molded or extruded thermoplasticarticle wherein said polyamide resin is selected from Group (IV)Polyamides and wherein said test temperature is at least 210° C. for atest period of at least 500 hours and said retention of tensile strengthis at least 70%, and more preferably at least 80% and 90%.

A further preferred embodiment is the molded or extruded thermoplasticarticle wherein said polyamide resin is selected from Group (V)Polyamides and wherein said test temperature is at least 230° C. for atest period of at least 500 hours and said retention of tensile strengthis at least 60%, and more preferably at least 70%, 80% and 90%.

The molded or extruded thermoplastic article comprises 0.25 to 15 weightpercent of one or more polyhydric alcohols having more than two hydroxylgroups and having a number average molecular weight (M_(n)) of less than2000 of less than 2000 as determined for polymeric materials with gelpermeation chromatography (GPC)

Polyhydric alcohols may be selected from aliphatic hydroxylic compoundscontaining more than two hydroxyl groups, aliphatic-cycloaliphaticcompounds containing more than two hydroxyl groups, cycloaliphaticcompounds containing more than two hydroxyl groups, aromatic andsaccharides.

An aliphatic chain in the polyhydric alcohol can include not only carbonatoms but also one or more hetero atoms which may be selected, forexample, from nitrogen, oxygen and sulphur atoms. A cycloaliphatic ringpresent in the polyhydric alcohol can be monocyclic or part of abicyclic or polycyclic ring system and may be carbocyclic orheterocyclic. A heterocyclic ring present in the polyhydric alcohol canbe monocyclic or part of a bicyclic or polycyclic ring system and mayinclude one or more hetero atoms which may be selected, for example,from nitrogen, oxygen and sulphur atoms. The one or more polyhydricalcohols may contain one or more substituents, such as ether, carboxylicacid, carboxylic acid amide or carboxylic acid ester groups.

Examples of polyhydric alcohol containing more than two hydroxyl groupsinclude, without limitation, triols, such as glycerol,trimethylolpropane, 2,3-di-(2-hydroxyethyl)-cyclohexan-1-ol,hexane-1,2,6-triol 1,1,1-tris-(hydroxymethyl)ethane,3-(2′-hydroxyethoxy)-propane-1,2-diol,3-(2′-hydroxypropoxy)propane-1,2-diol,2-(2′-hydroxyethoxy)-hexane-1,2-diol,6-(2′-hydroxypropoxy)-hexane-1,2-1,2-diol,1,1,1-tris-[(2′-hydroxyethoxy)-methyl]-ethane,1,1,1-tris[(2′-hydroxypropoxy)-methyl]-propane,1,1,1-tris-(4′-hydroxyphenyl)-ethane, 1,1,1-tris(hydroxyphenyl)-propane,1,3-tris-(dihydroxy-3-methylphenyl)-propane,1,1,4-tris-(dihydroxyphenyl)-butane,1,1,5-tris-(hydroxyphenyl)-3-methylpentane, di-trimethylopropane,trimethylolpropane ethoxylates, or trimethylolpropane propoxylates;polyols such as pentaerythritol, dipentaerythritol, andtripentaerythritol; and saccharides, such as cyclodextrin, D-mannose,glucose, galactose, sucrose, fructose, xylose, arabinose, D-mannitol,D-sorbitol, D- or L-arabitol, xylitol, iditol, talitol, allitol,altritol, guilitol, erythritol, threitol, and D-gulonic-y-lactone; andthe like.

Preferred polyhydric alcohols include those having a pair of hydroxylgroups which are attached to respective carbon atoms which are separatedone from another by at least one atom. Especially preferred polyhydricalcohols are those in which a pair of hydroxyl groups is attached torespective carbon atoms which are separated one from another by a singlecarbon atom.

Preferably, the polyhydric alcohol used in the thermoplastic compositionis pentaerythritol, dipentaerythritol, tripentaerythritol,di-trimethylolpropane, D-mannitol, D-sorbitol and xylitol. Morepreferably, the polyhydric alcohol used is dipentaerythritol and/ortripentaerythritol. A most preferred polyhydric alcohol isdipentaerythritol.

In various embodiments the content of said polyhydric alcohol in thethermoplastic composition is 0.25 to 15 weight percent, preferably 0.25to 8 weight percent, and more preferably 0.25 to 5, and 1 to 4 weightpercent.

The polyamide composition comprises 0.1 to 3 weight percent of one ormore co-stabilizer(s) having a 10% weight loss temperature, asdetermined by thermogravimetric analysis (TGA), of greater than 30degrees below the melting point of the polyamide resin, if a meltingpoint is present, or at least 250° C. if said melting point is notpresent, selected from the group consisting of secondary aryl amines andhindered amine light stabilizers (HALS), and mixtures thereof. For thepurposes of this invention, TGA weight loss will be determined accordingto ASTM D 3850-94, using a heating rate of 10° C./min, in air purgestream, with an appropriate flow rate of 0.8 mL/second. Theco-stabilizer preferably has a 10% weight loss temperature, asdetermined by TGA of at least 270° C., and more preferably 290° C., 320°C., and 340° C., and most preferably at least 350° C. The one or moreco-stabilizers preferably are present from at or about 0.1 to at orabout 1 weight percent, or more preferably from at or about 0.1 to at orabout 0.7 weight percent, based on the total weight of the polyamidecomposition.

Secondary aryl amines useful in the invention are high molecular weightorganic compound having low volatility. Preferably, the high molecularweight organic compound will be selected from the group consisting ofsecondary aryl amines further characterized as having a molecular weightof at least 260 g/mol and preferably at least 350 g/mol, together with a10% weight loss temperature as determined by thermogravimetric analysis(TGA) of at least 290° C., preferably at least 300° C., 320° C., 340°C., and most preferably at least 350° C.

By secondary aryl amine is meant an amine compound that contains twocarbon radicals chemically bound to a nitrogen atom where at least one,and preferably both carbon radicals, are aromatic. Preferably, at leastone of the aromatic radicals, such as, for example, a phenyl, naphthylor heteroaromatic group, is substituted with at least one substituentpreferably containing 1 to about 20 carbon atoms.

Examples of suitable secondary aryl amines include 4,4′di(α,α-dimethylbenzyl)diphenylamine available commercially as Naugard445 from Uniroyal Chemical Company, Middlebury, Conn.; the secondaryaryl amine condensation product of the reaction of diphenylamine withacetone, available commercially as Aminox from Uniroyal ChemicalCompany; and para-(paratoluenesulfonylamido)diphenylamine also availablefrom Uniroyal Chemical Company as Naugard SA. Other suitable secondaryaryl amines include N,N′-di-(2-naphthyl)-p-phenylenediamine, availablefrom ICI Rubber Chemicals, Calcutta, India. Other suitable secondaryaryl amines include 4,4′-bis(α,α′-tertiaryoctyl)diphenylamine,4,4′-bis(α-methylbenzhydryl)diphenylamine, and others from EP 0509282B1.

The hindered amine light stabilizers (HALS) may be one or more hinderedamine type light stabilizers (HALS).

HALS are compounds of the following general formulas and combinationsthereof:

In these formulas, R₁ up to and including R₅ are independentsubstituents. Examples of suitable substituents are hydrogen, ethergroups, ester groups, amine groups, amide groups, alkyl groups, alkenylgroups, alkynyl groups, aralkyl groups, cycloalkyl groups and arylgroups, in which the substituents in turn may contain functional groups;examples of functional groups are alcohols, ketones, anhydrides, imines,siloxanes, ethers, carboxyl groups, aldehydes, esters, amides, imides,amines, nitriles, ethers, urethanes and any combination thereof.

A hindered amine light stabilizer may also form part of a polymer oroligomer. Preferably, the HALS is a compound derived from a substitutedpiperidine compound, in particular any compound derived from analkyl-substituted piperidyl, piperidinyl or piperazinone compound, andsubstituted alkoxypiperidinyl compounds. Examples of such compounds are:2,2,6,6-tetramethyl-4-piperidone; 2,2,6,6-tetramethyl-4-piperidinol;bis-(1,2,2,66-pentamethylpiperidyl)-(3′,5′-di-tert-butyl-4-hydroxybenzyl) butylmalonate;di-(2,2,6,6-tetramethyl-4-piperidyl)sebacate (Tinuvin® 770, MW 481);oligomer of N-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol andsuccinic acid (Tinuvin® 622); oligomer of cyanuric acid andN,N-di(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylene diamine;bis-(2,2,6,6-tetramethyl-4-piperidinyl)succinate;bis-(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin®123); bis-(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate (Tinuvin® 765);Tinuvin® 144; Tinuvin® XT850;tetrakis-(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate;N,N′-bis-(2,2,6,6-tetramethyl-4-piperidyl)-hexane-1,6-diamine(Chimasorb® TS); N-butyl-2,2,6,6-tetramethyl-4-piperidinamine;2,2′-[(2,2,6,6-tetramethyl-piperidinyl)-imino]-bis-[ethanol];poly((6-morpholine-S-triazine-2,4-diyl)(2,2,6,6-tetramethyl-4-piperidinyl)-iminohexamethylene-(2,2,6,6-tetramethyl-4-piperidinyl)-imino)(Cyasorb® UV 3346);5-(2,2,6,6-tetramethyl-4-piperidinyl)-2-cyclo-undecyl-oxazole)(Hostavin® N20);1,1′-(1,2-ethane-di-yl)-bis-(3,3′,5,5′-tetramethyl-piperazinone);8-acetyl-3-dothecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro(4,5)decane-2,4-dione;polymethylpropyl-3-oxy-[4(2,2,6,6-tetramethyl)piperidinyl]siloxane(Uvasil® 299); 1,2,3,4-butane-tetracarboxylicacid-1,2,3-tris(1,2,2,6,6-pentamethyl-4-piperidinyl)-4-tridecylester;copolymer ofalpha-methylstyrene-N-(2,2,6,6-tetramethyl-4-piperidinyl)maleimide andN-stearyl maleimide; 1,2,3,4-butanetetracarboxylic acid, polymer withbeta,beta,beta′,beta′-tetramethyl-2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol,1,2,2,6,6-pentammethyl-4-piperidinyl ester (Mark® LA63);2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diethanol,beta,beta,beta′,beta′-tetramethyl-polymerwith 1,2,3,4-butanetetracarboxylic acid,2,2,6,6-tetramethyl-4-piperidinyl ester (Mark® LA68); D-glucitol,1,3:2,4-bis-O-(2,2,6,6-tetramethyl-4-piperidinylidene)-(HALS 7);oligomer of7-oxa-3,20-diazadispiro[5.1.11.2]-heneicosan-21-one-2,2,4,4-tetramethyl-20-(oxiranylmethyl)(Hostavin® N30); propanedioic acid,[(4-methoxyphenyl)methylene]-,bis(1,2,2,6,6-pentamethyl-4-piperidinyl)ester(Sanduvor® PR 31); formamide,N,N′-1,6-hexanediylbis[N-(2,2,6,6-tetramethyl-4-piperidinyl (Uvinul®4050H); 1,3,5-triazine-2,4,6-triamine,N,N′″-[1,2-ethanediylbis[[[4,6-bis[butyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amino]-1,3,5-triazine-2-yl]imino]-3,1-propanediyl]]-bis[N′,N″-dibutyl-N′,N″-bis(1,2,2,6,6-pentamethyl-4-piperidinyl) (Chimassorb® 119 MW 2286);poly[[6-[(1,1,3,33-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-peperidinyl)-imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]](Chimassorb®944 MW 2000-3000): 1,5-dioxaspiro(5,5) undecane 3,3-dicarboxylic acid,bis(2,2,6,6-tetramethyl-4-peridinyl)ester (Cyasorb® UV-500);1,5-dioxaspiro(5,5)undecane 3,3-dicarboxylic acid, bis(1,2,2,6,6-pentamethyl-4-peridinyl)ester (Cyasorb® UV-516);N-2,2,6,6-tetramethyl-4-piperidinyl-N-amino-oxamide;4-acryloyloxy-1,2,2,6,6-pentamethyl-4-piperidine.1,5,8,12-tetrakis[2′,4′-bis(1″,2″,2″,6″,6″-pentamethyl-4″-piperidinyl(butyl)amino)-1′,3′,5′-triazine-6′-yl]-1,5,8,12-tetraazadodecane;HALS PB-41 (Clariant Huningue S. A.); Nylostab® S-EED (Clariant HuningueS. A.);3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidyl)-pyrrolidin-2,5-dione;Uvasorb® HA88;1,1′-(1,2-ethane-di-yl)-bis-(3,3′,5,5′-tetra-methyl-piperazinone)(Good-rite® 3034);1,1′1″-(1,3,5-triazine-2,4,6-triyltris((cyclohexylimino)-2,1-ethanediyl)tris(3,3,5,5-tetramethylpiperazinone)(Good-rite® 3150) and;1,1′,1″-(1,3,5-triazine-2,4,6-triyltris((cyclohexylimino)-2,1-ethanediyl)tris(3,3,4,5,5-tetramethylpiperazinone)(Good-rite® 3159), (Tinuvin® and Chimassorb® materials are availablefrom Ciba Specialty Chemicals; Cyasorb® materials are available fromCytec Technology Corp.; Uvasil® materials are available from Great LakesChemical Corp.; Saduvor®, Hostavin®, and Nylostab® materials areavailable from Clariant Corp.; Uvinul® materials are available fromBASF; Uvasorb® materials are available from Partecipazioni Industriali:and Good-rite® materials are available from B.F. Goodrich Co. Mark®materials are available from Asahi Denka Co.)

Preferred HALS include high-molecular weight oligomeric or polymericHALS having a molecular weight of more than about 1000, and preferablymore than about 2000.

Other specific HALS are selected from the group consisting ordi-(2,2,6,6-tetramethyl-4-piperidyl) sebacate (Tinuvin® 770, MW 481)Nylostab® S-EED (Clariant Huningue S. A.);1,3,5-triazine-2,4,6-triamine, N,N′″-[1,2-ethanediylbis[[[4,6-bis[butyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amino]-1,3,5-triazine-2-yl]imino]-3,1-propanediyl]]-bis[N′,N″-dibutyl-N′,N″-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)(Chimassorb® 119 MW 2286); andpoly[[6-[(1,1,3,33-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-peperidinyl)-imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]](Chimassorb®944 MW 2000-3000).

Mixtures of secondary aryl amines and HALS may be used. A preferredembodiment comprises at least two co-stabilizers, at least one selectedfrom the secondary aryl amines; and at least one selected from the groupof HALS, as disclosed above, wherein the total weight percent of themixture of co-stabilizers is at least 0.5 wt percent, and preferably atleast 0.9 weight percent.

The molded or extruded thermoplastic article comprises 10 to about 60weight percent, and preferably about 12.5 to 55 weight percent and 15 to50 weight percent, of one or more reinforcement agents. Thereinforcement agent may be any filler, but is preferably selected fromthe group consisting calcium carbonate, glass fibers with circular andnoncircular cross-section, glass flakes, glass beads, carbon fibers,talc, mica, wollastonite, calcined clay, kaolin, diatomite, magnesiumsulfate, magnesium silicate, barium sulfate, titanium dioxide, sodiumaluminum carbonate, barium ferrite, potassium titanate and mixturesthereof.

Glass fibers with noncircular cross-section refer to glass fiber havinga cross section having a major axis lying perpendicular to alongitudinal direction of the glass fiber and corresponding to thelongest linear distance in the cross section. The non-circular crosssection has a minor axis corresponding to the longest linear distance inthe cross section in a direction perpendicular to the major axis. Thenon-circular cross section of the fiber may have a variety of shapesincluding a cocoon-type (figure-eight) shape, a rectangular shape; anelliptical shape; a roughly triangular shape; a polygonal shape; and anoblong shape. As will be understood by those skilled in the art, thecross section may have other shapes. The ratio of the length of themajor axis to that of the minor access is preferably between about 1.5:1and about 6:1. The ratio is more preferably between about 2:1 and 5:1and yet more preferably between about 3:1 to about 4:1. Suitable glassfiber are disclosed in EP 0 190 001 and EP 0 196 194.

The molded or extruded thermoplastic article, optionally, comprises 0 to50 weight percent of a polymeric toughener comprising a reactivefunctional group and/or a metal salt of a carboxylic acid. In oneembodiment the molded or extruded thermoplastic article comprises 2 to20 weight percent polymeric toughener selected from the group consistingof: a copolymer of ethylene, glycidyl(meth)acrylate, and optionally oneor more (meth)acrylate esters; an ethylene/α-olefin orethylene/α-olefin/diene copolymer grafted with an unsaturated carboxylicanhydride; a copolymer of ethylene, 2-isocyanatoethyl(meth)acrylate, andoptionally one or more (meth)acrylate esters; and a copolymer ofethylene and acrylic acid reacted with a Zn, Li, Mg or Mn compound toform the corresponding ionomer.

In the present invention, the polyamide composition may also compriseother additives commonly used in the art, such other heat stabilizers orantioxidants, antistatic agents, blowing agents, lubricants,plasticizers, and colorant and pigments.

Other heat stabilizers include copper stabilizers and hindered phenols,and mixtures thereof.

A significant advantage of the molded or extruded thermoplastic articlesof the invention is that high thermal stability is provided without theuse of conventional copper heat stabilizers. Copper heat stabilizerstend to act as corrosive agents over long periods of time at elevatedtemperatures; and in some environments actually cause degradation ofsemiaromatic polymers. Thus, another embodiment is molded or extrudedthermoplastic article wherein said polyamide composition comprises lessthan 25 ppm copper as determined with atomic absorption spectroscopy.

Herein the polyamide composition is a mixture by melt-blending, in whichall polymeric ingredients are adequately mixed, and all non-polymericingredients are adequately dispersed in a polymer matrix. Anymelt-blending method may be used for mixing polymeric ingredients andnon-polymeric ingredients of the present invention. For example,polymeric ingredients and non-polymeric ingredients may be fed into amelt mixer, such as single screw extruder or twin screw extruder,agitator, single screw or twin screw kneader, or Banbury mixer, and theaddition step may be addition of all ingredients at once or gradualaddition in batches. When the polymeric ingredient and non-polymericingredient are gradually added in batches, a part of the polymericingredients and/or non-polymeric ingredients is first added, and then ismelt-mixed with the remaining polymeric ingredients and non-polymericingredients that are subsequently added, until an adequately mixedcomposition is obtained. If a reinforcing filler presents a longphysical shape (for example, a long glass fiber), drawing extrusionmolding may be used to prepare a reinforced composition.

The polyamide composition having a polyhydroxy polymer, as disclosedabove, is useful in increasing long-term heat stability at hightemperatures of molded or extruded articles made therefrom. Thelong-term heat stability of the articles can be assessed by exposure(air oven ageing) of 4 mm thick test samples at various testtemperatures in an oven for various test periods of time. The oven testtemperatures for the composition disclosed herein include 170° C. and500 hours test periods; 210° C. and 500 hours test periods; and 230° C.and 500 hours test periods. The test samples, after air oven ageing, aretested for tensile strength and elongation to break, according to ISO527-2/1A test method; and compared with unexposed controls havingidentical composition and shape, that are dry as molded (DAM). Thecomparison with the DAM controls provides the retention of tensilestrength and/or retention of elongation to break, and thus the variouscompositions can be assessed as to long-term heat stability performance.

In various embodiments the thermoplastic polyamide composition has anAOA 170° C./500 hours retention of tensile strength of at least 50% andpreferably at least 60, 70, 80, and 90%, based upon comparison with DAMnon-exposed controls.

In various embodiments the thermoplastic polyamide composition has anAOA 210° C./500 hours retention of tensile strength of at least 50% andpreferably at least 70, 80, and 90%, based upon comparison with DAMnon-exposed controls.

In another aspect, the present invention relates a use of the abovedisclosed polyamide compositions for high temperature applications.

In another aspect, the present invention relates to a method formanufacturing an article by shaping the thermoplastic composition of theinvention. Examples of articles are films or laminates, automotive partsor engine parts or electrical/electronics parts. By “shaping”, it ismeant any shaping technique, such as for example extrusion, injectionmoulding, thermoform moulding, compression moulding or blow moulding.Preferably, the article is shaped by injection moulding or blowmoulding.

The molded or extruded thermoplastic articles disclosed herein may haveapplication in many vehicular components that meet one or more of thefollowing requirements: high impact requirements; significant weightreduction (over conventional metals, for instance); resistance to hightemperature; resistance to oil environment; resistance to chemicalagents such as coolants; and noise reduction allowing more compact andintegrated design. Specific molded or extruded thermoplastic articlesare selected from the group consisting of charge air coolers (CAC);cylinder head covers (CHC); oil pans; engine cooling systems, includingthermostat and heater housings and coolant pumps; exhaust systemsincluding mufflers and housings for catalytic converters; air intakemanifolds (AIM); and timing chain belt front covers. As an illustrativeexample of desired mechanical resistance against long-term hightemperature exposure, a charge air cooler can be mentioned. A charge aircooler is a part of the radiator of a vehicle that improves enginecombustion efficiency. Charge air coolers reduce the charge airtemperature and increase the density of the air after compression in theturbocharger thus allowing more air to enter into the cylinders toimprove engine efficiency. Since the temperature of the incoming air canbe more than 200° C. when it enters the charge air cooler, it isrequired that this part be made out of a composition maintaining goodmechanical properties under high temperatures for an extended period oftime.

The present invention is further illustrated by the following examples.It should be understood that the following examples are for illustrationpurposes only, and are not used to limit the present invention thereto.

EXAMPLES Methods

Compounding Method

All Examples and Comparative Examples were prepared by melt blending theingredients listed in the Tables in a 30 mm twin screw extruder (ZSK 30by Coperion) operating at about 310° C. barrel setting using a screwspeed of about 300 rpm, a throughput of 13.6 kg/hour and a melttemperature measured by hand of about 355° C. The glass fibers wereadded to the melt through a screw side feeder. Ingredient quantitiesshown in the Tables are given in weight percent on the basis of thetotal weight of the thermoplastic composition.

The compounded mixture was extruded in the form of laces or strands,cooled in a water bath, chopped into granules and placed into sealedaluminum lined bags in order to prevent moisture pick up. The coolingand cutting conditions were adjusted to ensure that the materials werekept below 0.15 wt % of moisture level.

Physical Properties Measurement

Mechanical tensile properties, i.e., E-modulus, stress at break (Tensilestrength) and strain at break (elongation at break) were measuredaccording to ISO 527-2/1A. Measurements were made on injection moldedISO tensile bars. Mold temperature for PA 6/DT test specimens was145-150° C.; mold temperature for PA 6T/66 test specimens was 90-100°C.; and melt temperature was 325-330° C. for both resins.

The thickness of the test specimens was 4 mm and a width of 10 mmaccording to ISO 527/1A at a testing speed of 5 mm/min (tensile strengthand elongation). Tensile Modulus was measured at 1 mm/min.

Air Oven Ageing (AOA)

The test specimens were heat aged in a re-circulating air ovens (Heraeustype UT6060) according to the procedure detailed in ISO 2578. At variousheat aging times, the test specimens were removed from the oven, allowedto cool to room temperature and sealed into aluminum lined bags untilready for testing, The tensile mechanical properties were then measuredaccording to ISO 527 using a Zwick tensile instrument. The averagevalues obtained from 5 specimens are given in the Tables.

Retention of tensile strength (TS) and elongation at break (EL)corresponds to the percentage of the tensile strength and elongation atbreak after heat aging for 500 hours 1000 hours in comparison with thevalue of specimens non-heat-aged control specimens considered as being100%.

Materials

PA6T/66 refers HTN502 NC010, a copolyamide made from terephthalic acid,adipic acid, and hexamethylenediamine; wherein the two acids are used ina 55:45 molar ratio: having a melting point of ca. 310° C., having aninherent viscosity (IV), according to ASTM D2857 method, in the range of0.9 to 1.0 (typically 0.96) available from E.I. DuPont de Nemours andCompany, Wilmington, Del., USA.

PA6T/DT refers HTN501 NC010, a copolyamide of terephthalic acid,hexamethylenediamine, and 2-methyl-pentamethylenediamine having aninherent viscosity (IV), according to ASTM D2857 method, in the range of0.8 to 0.95 (typically 0.88) and a melting point of about 300° C., andavailable from E.I. DuPont de Nemours and Company, Wilmington, Del.,USA.

DPE refers to dipentaerythritol that was from Perstorp SpecialityChemicals AB, Perstorp, Sweden as Di-Penta 93,

TPE refers to tripentaerythritol that was from Sigma Aldrich Co.,Milwaukee Wis.

Glass Fiber D refers to PPG 3540 chopped glass fiber available from PPGindustries, Pittsburgh, Pa.

Naugard® 445 hindered amine refers to 4,4′di(.α,α-dimethylbenzyl)diphenylamine available commercially fromUniroyal Chemical Company, Middlebury, Conn.

Irganox® 1010 stabilizer was available from Ciba Speciality ChemicalsInc, Switzerland.

Irganox® 1098 stabilizer was available from Ciba Speciality ChemicalsInc, Switzerland.

Chimassorb® 944 refers to(poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)-imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]]), supplied by Ciba SpecialtyChemicals.

Chimassorb® 119 is (1,3,5-triazine-2,4,6-triamine,N,N′″-[1,2-ethanediylbis[[[4,6-bis[butyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amino]-1,3,5-triazine-2-yl]imino]-3,1-propanediyl]]-bis[N′,N″-dibutyl-N′,N″-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)),supplied by Ciba Specialty Chemicals.

Wax OP is a lubricant manufactured by Clariant Corp., Charlotte, N.C.

Black Pigment B refers to 25 wt % carbon black in PA6 polymer.

Example 1 and C-1-C-5

Compositions of Examples 1 and Comparative Examples C-1-C-5 are listedin Table 1 for PA6T/DT compositions. Tensile properties after AOA at210° C. and 230° C. at 500 h and 1000 h, and retention of physicalproperties are listed in Table 1. Higher values of tensile strength (TS)mean better mechanical properties. Higher % retention of tensilestrength indicate a higher thermal stability.

Data in Table 1 indicates that Example 1 having 1.5 wt % DPE and 1 wt %Naugard® 445 hindered amine has higher % retention of tensile strengththan the Comparative Examples containing Naugard alone; copper heatstabilizer alone; 1.5 wt % DPE alone; or Naugard® 445 hindered aminealone. Example 1 shows surprising and unexpected results, indicated bythe much higher % retention of tensile strength under AOA at 230°C./1000 hours, as compared to conventional copper stabilizer commonlyused in commercial products.

Example 2 and C-6-C-10

Compositions of Examples 2 and Comparative Examples C-6-C-10 are listedin Table 2 for PA6T/DT compositions. Tensile properties after AOA at210° C. and 230° C. at 500 h and 1000 h, and retention of physicalproperties are listed in Table 2

Data in Table 2 indicates that Example 2 having 2 wt % TPE, 0.5 wt %Naugard® 445 hindered amine, and 0.5 wt % Chimassorb® 944FDL has higher% retention of tensile strength than the Comparative Examples containing2.0 wt % TPF alone; Chimassorb® 944FDL; or Naugard® 445 hindered aminealone.

TABLE 1 Example C-1 C-2 C-3 C-4 C-5 1 PA6T/DT 64.75 64.05 63.25 61.7563.75 62.25 DPE 1.5 3 1.5 Cu heat 0.7 stabilizer Naugard 445 1 1 Wax OP0.25 0.25 0.25 0.25 0.25 0.25 Glass Fiber D 35 35 35 35 35 35 AOA 210°C. TS (MPa) 0 h 225 223 214 212 214 219 TS (MPa) 500 115 141 218 218 150220 h TS (MPa) 1000 98 130 210 208 133 207 h 500 hrs TS 51 63 102 103 70100 Retention (%) 1000 hrs TS 44 58 98 98 62 95 Retention (%) El (%) 0 h2.3 2.4 2.2 2.2 2.2 2.2 El (%) 500 h 1.2 1.4 2.2 2.2 1.5 2.2 El (%) 1000h 0.9 1.3 2.1 2.1 1.3 2.1 500 hrs El 52 58 100 100 68 100 Retention (%)1000 hrs El 39 54 95 95 59 95 Retention (%) AOA 230° C. TS (MPa) 0 h 225223 214 212 214 219 TS (MPa) 500 75 125 135 172 112 165 h TS (MPa) 100020 91 115 156 52 141 h 500 hrs TS 33 56 63 81 52 75 Retention (%) 1000hrs TS 9 41 54 74 24 64 Retention (%) El (%) 0 h 2.3 2.4 2.2 2.2 2.2 2.2El (%) 500 h 0.8 1.1 1.3 1.8 1.2 1.7 El (%) 1000 h 0.3 0.8 1.2 1.7 0.41.4 500 hrs El 35 46 59 82 55 77 Retention (%) 1000 hrs El 13 33 55 7718 64 Retention (%) In all Tables: TS = tensile strength; EL =elongation to break

TABLE 2 Example C-6 C-7 C-8 C-9 C-10 2 PA6T/DT 63.75 62.75 61.75 64.2564.25 61.75 TPE 1 2 3 2 Naugard ® 0.5 0.5 445 Chimassorb ® 0.5 0.5944FDL Wax OP 0.25 0.25 0.25 0.25 0.25 0.25 Glass Fiber D 35 35 35 35 3535 AOA 210° C. TS (MPa) 0 h 218 218 215 228 220 221 TS (MPa) 500 186 220213 128 144 223 h TS (MPa) 1000 152 210 207 115 131 212 h 500 hrs TS 85101 99 56 65 101 Retention (%) 1000 hrs TS 70 96 96 50 60 96 Retention(%) El (%) 0 h 2.2 2.2 2.2 2.2 2.2 2.2 El (%) 500 h 1.8 2.2 2.2 1.2 1.52.2 El (%) 1000 h 1.5 2.1 2.1 1.1 1.2 2.1 500 hrs El 82 100 100 55 68100 Retention (%) 1000 hrs El 68 95 95 50 55 95 Retention (%) AOA 230°C. TS (MPa) 0 h 218 218 215 228 220 221 TS (MPa) 500 135 158 177 88 98178 h TS (MPa) 1000 128 142 152 38 44 162 h 500 hrs TS 62 72 82 39 45 81Retention (%) 1000 hrs TS 59 65 71 17 20 73 Retention (%) El (%) 0 h 2.22.2 2.2 2.2 2.2 2.2 El (%) 500 h 1.2 1.7 1.7 0.9 0.7 1.8 El (%) 1000 h1.1 1.4 1.5 0.3 0.4 1.6 500 hrs El 55 77 77 41 32 82 Retention (%) 1000hrs El 50 64 68 14 18 73 Retention (%)

Example 3 and C-11-C-14

Compositions of Examples 3 and Comparative Examples C-1-C-14 are listedin Table 3 for PA6T/66 compositions. Tensile properties after AOA at210° C. and 230° C. at 500 h and 1000 h, and retention of physicalproperties are listed in Table 3

Data in Table 3 indicates that Example 3 having 2 wt % DPE and 0.5 wt %Naugard® 445 hindered amine has higher % retention of tensile strengththan the Comparative Examples containing 2.0 wt % DPE alone; Naugard®445 hindered amine alone; or a combination of Naugard® 445 hinderedamine and Irganox® 1098 hindered phenol.

TABLE 3 Example C-11 C-12 C-13 C-14 3 PA6T/66 64.35 64.25 63.95 62.7562.25 DPE 2.00 2.00 Naugard 445 0.50 0.50 0.50 Wax OP 0.25 0.26 0.250.25 0.25 Irganox 1098 0.30 Cu heat stabilizer 0.40 Glass Fiber D 35.0035.00 35.00 35.00 35.00 AOA 210° C. TS (MPa) 0 h 202 205 204 202 201 TS(MPa) 500 h 135 132 128 185 207 TS (MPa) 1000 h 126 128 115 176 191 500hrs TS Retention (%) 67 64 63 92 103 1000 hrs TS Retention 62 62 56 8795 (%) El (%) 0 h 2.2 2.3 23 2.1 2.1 El (%) 500 h 1.4 1.4 1.4 1.9 2.3 El(%) 1000 h 1.2 1.1 1.1 1.8 2.0 500 hrs El Retention (%) 64 61 61 90 1101000 hrs El Retention 65 48 48 86 95 (%) AOA 230° C. TS (MPa) 0 h 202205 204 202 201 TS (MPa) 500 h 131 75 88 162 184 TS (MPa) 1000 h 100 2526 148 165 500 hrs TS Retention (%) 65 37 43 80 92 1000 hrs TS Retention50 12 13 73 82 (%) El (%) 0 h 2.2 2.3 2.3 2.1 2.1 El (%) 500 h 1.4 0.81.8 1.8 1.9 El (%) 1000 h 1.0 0.3 0.3 1.5 1.6 500 hrs El Retention (%)64 35 78 86 90 1000 hrs El Retention 45 13 13 71 76 (%)

Example 4-7

Compositions of Examples 4-7 are listed in Table 4 for PA6T/66compositions with various co-stabilizers in combination with 2 w % TPE.Tensile properties after AA at 210° C. and 230° C. at 500 h and 1000 h,and retention of physical properties are listed in Table 4. Examples 4-7all show unexpectedly high retention of tensile strength under AOA 230°C./1000 hour ageing as compared with C-11 having a conventional copperheat stabilizer.

TABLE 4 Example 4 5 6 7 PA6T/66 62.25 61.75 61.25 61.75 Chimassorb ®944FD 0.50 TPE 2.00 2.00 2.00 2.00 Chimassorb ® 119FL 0.50 1.00Naugard ® 445 0.50 0.50 0.50 0.50 Wax OP 0.25 0.25 0.25 0.25 Glass FiberD 35.00 35.00 35.00 35.00 AOA 210° C. TS (MPa) 0 h 205 212 211 209 TS(MPa) 500 h 195 215 218 211 TS (MPa) 1000 h 192 214 210 210 500 hrs TSRetention (%) 95 101 103 101 1000 hrs TS Retention (%) 94 101 100 100 El(%) 0 h 2.3 2.4 2.2 2.2 El (%) 500 h 2.2 2.4 2.5 2.3 El (%) 1000 h 2.22.4 2.4 2.2 AOA 230° C. 500 hrs El Retention (%) 96 100 114 105 1000 hrsEl Retention (%) 96 100 109 100 TS (MPa) 0 h 205 212 211 209 TS (MPa)500 h 185 214 209 211 TS (MPa) 1000 h 158 199 191 188 500 hrs TSRetention (%) 90 101 99 101 1000 hrs TS Retention (%) 77 94 91 90 El (%)0 h 2.3 2.4 2.2 2.2 El (%) 500 h 1.9 2.3 2.3 2.2 El (%) 1000 h 1.5 2.12.1 2.0 500 hrs El Retention (%) 83 96 105 100 1000 hrs El Retention (%)65 88 95 91

Example 8-10

Compositions of Examples 8-10 are listed in Table 5 for PA6T/66compositions with various co-stabilizers in combination with 2 wt % TPE.Tensile properties after AOA at 210° C. and 230° C. at 500 h and 1000 h,and retention of physical properties are listed in Table 5.

TABLE 5 Example 8 9 10 PA6T/66 61.25 61.75 61.25 Chimassorb ® 944FD 1.00TPE 2.00 2.00 2.00 Chimassorb ® 119FL Naugard ® 445 0.50 0.50 0.50Tinuvin ® 770DF 0.50 1.00 Wax OP 0.25 0.25 0.25 Glass Fiber D 35.0035.00 35.00 AOA 210° C. TS (MPa) 0 h 212 202 201 TS (MPa) 500 h 225 208208 TS (MPa) 1000 h 209 202 199 500 hrs TS Retention (%) 106 103 1031000 hrs TS Retention (%) 99 100 99 El (%) 0 h 2.3 2.2 2.2 El (%) 500 h2.4 2.2 2.3 El (%) 1000 h 2.3 2.1 2.2 500 hrs El Retention (%) 104 100105 1000 hrs El Retention (%) 100 95 100 AOA 230° C. TS (MPa) 0 h 212202 201 TS (Mpa) 500 h 215 208 207 TS (MPa) 1000 h 184 182 181 500 hrsTS Retention (%) 101 103 103 1000 hrs TS Retention (%) 87 90 90 El (%) 0h 2.3 2.2 2.2 El (%) 500 h 2.2 2.3 2.3 El (%) 1000 h 2 1.9 1.9 500 hrsEl Retention (%) 96 105 105 1000 hrs El Retention (%) 87 86 86

Example 11-13 and C-15

Compositions of Examples 11-13 are listed in Table 6 for PA6T/66compositions with various co-stabilizers in combination with 3 wt % DPE.Tensile properties after AOA at 210° C. and 230° C. at 500 h and 1000 h,and retention of physical properties are listed in Table 5.

Examples 11-13 all show unexpected and surprising retention of tensilestrength under AOA 230° C./1000 hour ageing as compared with C-15 havinga conventional copper heat stabilizer.

TABLE 6 Example 11 12 13 C-15 PA6T/66 61.25 60.75 60.75 64.35Chimassorb ® 944FD 0.50 DPE 3.00 3.00 3.00 Chimassorb ® 119FL 0.50Naugard ® 445 0.50 0.50 0.50 Wax OP 0.25 0.25 0.25 0.25 Cu heatstabilizer 0.40 Glass Fiber D 35.00 35.00 35.00 35.00 AOA 210° C. TS(MPa) 0 h 208 211 210 220 TS (MPa) 500 h 215 225 226 167 TS (MPa) 1000 h209 215 218 134 500 hrs TS Retention (%) 103 107 108 76 1000 hrs TSRetention (%) 100 102 104 61 El (%) 0 h 2.2 2.1 2.3 2.2 El (%) 500 h 2.32.3 2.4 1.8 El (%) 1000 h 2.2 2.2 2.3 1.3 500 hrs El Retention (%) 105110 104 82 1000 hrs El Retention (%) 100 105 100 59 AOA 230° C. TS (MPa)0 h 208 211 210 220 TS (MPa) 500 h 202 215 218 138 TS (MPa) 1000 h 181214 211 98 500 hrs TS Retention (%) 97 102 104 63 1000 hrs TS Retention(%) 87 101 100 45 El (%) 0 h 2.2 2.1 2.3 2.2 El (%) 500 h 2.2 2.2 2.21.5 El (%) 1000 h 1.9 2.2 2.2 1.0 500 hrs El Retention (%) 100 105 96 681000 hrs El Retention (%) 86 105 96 45

Comparative Examples C-1-C-20

Comparative Examples C-16-C-20 are listed in Table 7 for PA6T/66compositions with various co-stabilizers, but without a polyhydricalcohol. Tensile properties after AOA at 210° C. and 230° C. at 500 hand 1000 h, and retention of physical properties are listed in Table 7.The various combinations of co-stabilizers fail to provide highretention of tensile strength under AOA at 230 C/1000 hours, as comparedto the Examples 4-13. For instance Examples 4-13, having a combinationof polyhydric alcohol and co-stabilizer, show retention of tensilestrength of at least 77% in all examples at AOA of 230 C/1000 hours;whereas the comparative examples, show a maximum of only 44% under thesame conditions.

TABLE 7 Example C-16 C-17 C-18 C-19 C-20 PA6T/66 64.25 63.75 63.25 63.7563.3 Chimassorb ® 944FD 0.50 1.00 Chimassorb ® 119FL 0.50 1.00 Naugard ®445 0.50 0.50 0.50 0.50 0.50 Wax OP 0.25 0.25 0.25 0.25 0.25 Glass FiberD 35.00 35.00 35.00 35.00 35.00 210° C. TS (MPa) 0 h 222 221 218 216 215TS (MPa) 500 h 138 133 138 121 88 TS (MPa) 1000 h 118 62 52 48 41 500hrs TS Retention (%) 62 60 63 56 41 1000 hrs TS Retention 53 28 24 22 19(%) El (%) 0 h 2.2 2.3 2.3 2.2 2.1 El (%) 500 h 1.3 1.3 1.3 1.2 0.9 El(%) 1000 h 1.1 0.6 0.5 0.5 0.5 500 hrs El Retention (%) 59 57 57 55 431000 hrs El Retention 50 26 22 23 24 (%) AOA 230° C. TS (MPa) 0 h 222221 218 216 215 TS (MPa) 500 h 125 118 109 94 71 TS (MPa) 1000 h 91 5848 45 32 500 hrs TS Retention (%) 56 53 50 44 33 1000 hrs TS Retention41 26 22 21 15 (%) El (%) 0 h 2.2 2.3 2.3 2.2 2.1 El (%) 500 h 1.2 1.11.1 0.9 0.8 El (%) 1000 h 0.9 0.6 0.5 0.5 0.3 500 hrs El Retention (%)55 48 48 41 38 1000 hrs El Retention 41 26 22 23 14 (%)

The Examples illustrate polyhydric alcohols in combination withco-stabilizers, added to reinforced polyamide compositions are aneconomically viable solution to the current need of having articles thatare highly heat resistant upon long-term exposure in comparison withconventional heat stabilizers that lead either to poor heat agingresistant compositions or expensive ones.

1-15. (canceled)
 16. A molded or extruded thermoplastic articlecomprising a polyamide composition comprising: (a) at least onepolyamide resin having a melting point and/or glass transitiontemperature, selected from the group consisting of: (I) Group (III)Polyamides having the melting point of at least 210° C., and comprising:(aa) about 20 to about 35 mole percent semiaromatic repeat units derivedfrom monomers selected from one or more of the group consisting of: (i)aromatic dicarboxylic acids having 8 to 20 carbon atoms and aliphaticdiamines having 4 to 20 carbon atoms; and (bb) about 65 to about 80 molepercent aliphatic repeat units derived from monomers selected from oneor more of the group consisting of: (ii) an aliphatic dicarboxylic acidhaving 6 to 20 carbon atoms and the aliphatic diamine having 4 to 20carbon atoms; (iii) a lactam and/or aminocarboxylic acid having 4 to 20carbon atoms; (II) Group (IV) Polyamides comprising: (cc) about 50 toabout 95 mole percent semiaromatic repeat units derived from monomersselected from one or more of the group consisting of: (i) aromaticdicarboxylic acids having 8 to 20 carbon atoms and aliphatic diamineshaving 4 to 20 carbon atoms; and (dd) about 5 to about 50 mole percentaliphatic repeat units derived from monomers selected from one or moreof the group consisting of: (ii) an aliphatic dicarboxylic acid having 6to 20 carbon atoms and the aliphatic diamine having 4 to 20 carbonatoms; (iii) a lactam and/or aminocarboxylic acid having 4 to 20 carbonatoms; (III) Group (V) Polyamides having the melting point of at least260° C., and comprising: (ee) greater than 95 mole percent semiaromaticrepeat units derived from monomers selected from one or more of thegroup consisting of: (i) aromatic dicarboxylic acids having 8 to 20carbon atoms and aliphatic diamines having 4 to 20 carbon atoms; (ff)less than 5 mole percent aliphatic repeat units derived from monomersselected from one or more of the group consisting of: (ii) an aliphaticdicarboxylic acid having 6 to 20 carbon atoms and the aliphatic diaminehaving 4 to 20 carbon atoms; (iii) a lactam and/or aminocarboxylic acidhaving 4 to 20 carbon atoms; (IV) and mixtures of Group (III)Polyamides, Group (IV) Polyamides, and Group (V) Polyamides; (b) 1 to 4weight percent of at least one polyhydric alcohol selected from thegroup consisting of pentaerythritol, dipentaerythritol,tripentaerythritol, di-trimethylopropane, D-mannitol, D-sorbitol,xylitol, and mixtures thereof; (c) 0.1 to 3 weight percent of at leastone co-stabilizer having a 10% weight loss temperature, as determined bythermogravimetric analysis, of greater than 30° C. below the meltingpoint of the polyamide resin if the melting point is present, or atleast 250° C. if the melting point is not present; selected from thegroup consisting of secondary aryl amines, hindered amine lightstabilizers, and mixtures thereof; (d) 10 to 60 weight percent of atleast one reinforcement agent; and (e) 0 to 50 weight percent of atleast one polymeric toughener comprising a reactive functional group, ametal salt of a carboxylic acid, or mixtures thereof; wherein all weightpercentages are based on the total weight of the polyamide composition;and wherein 4 mm test bars prepared from the polyamide composition,exposed at a test temperature at 230° C. for a test period of 500 hours,in an atmosphere of air, and tested according to ISO 527-2/1A, have aretention of tensile strength, on average, of at least 60 percent, ascompared with that of an unexposed control of identical composition andshape.
 17. The molded or extruded thermoplastic article of claim 16,wherein the polyamide resin comprises a blend of two or more polyamidesselected from the group consisting of Group (III) and Group (VI)Polyamides, and Group (IV) and Group (V) Polyamides.
 18. The molded orextruded thermoplastic article of claim 16, wherein the polyamide resinis selected from poly(hexamethylene terephthalamide/hexamethylenehexanediamide) (PA6T/66), poly(hexamethyleneterephthalamide/2-methylpentamethylene terephthalamide) (PA6T/DT), ormixtures thereof.
 19. The molded or extruded thermoplastic article ofclaim 16, wherein the polyhydric alcohol is selected from the groupconsisting of dipentaerythritol, tripentaerythritol, and mixturesthereof.
 20. The molded or extruded thermoplastic article of claim 16,wherein the co-stabilizer is at least one secondary aryl amine.
 21. Themolded or extruded thermoplastic article of claim 16, wherein thereinforcement agent is selected from the group consisting calciumcarbonate, glass fibers with circular and noncircular cross-section,glass flakes, glass beads, carbon fibers, talc, mica, wollastonite,calcined clay, kaolin, diatomite, magnesium sulfate, magnesium silicate,barium sulphate, titanium dioxide, sodium aluminum carbonate, bariumferrite, potassium titanate, and mixtures thereof.
 22. The molded orextruded thermoplastic article of claim 16, wherein the polyamidecomposition comprises less than 25 ppm copper, as determined with atomicabsorption spectroscopy.
 23. The molded or extruded thermoplasticarticle of claim 16, wherein the article is selected from the groupconsisting of charge air coolers; cylinder head covers; oil pans; enginecooling systems, thermostat and heater housings, coolant pumps,mufflers, housings for catalytic converters; air intake manifolds; andtiming chain belt front covers.
 24. The molded or extruded thermoplasticarticle of claim 16, wherein the co-stabilizer is selected from 4,4′di(α,α-dimethylbenzyl)diphenylamine;(poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidinyl)-imino]-1,6-hexanediyl[(2,2,6,6-tetramethyl-4-piperidinyl)imino]]);(1,3,5-triazine-2,4,6-triamine,N,N′″-[1,2-ethanediylbis[[[4,6-bis[butyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amino]-1,3,5-triazine-2-yl]imino]-3,1-propanediyl]]-bis[N′,N″-dibutyl-N′,N″-bis(1,2,2,6,6-pentamethyl-4-piperidinyl));di-(2,2,6,6-tetramethyl-4-piperidyl) sebacate; and mixtures thereof. 25.The molded or extruded thermoplastic article of claim 16, wherein thetest period is a long-term test period equal to, or longer than, 1000hours.
 26. The molded or extruded thermoplastic article of claim 16,wherein the retention of tensile strength, on average, is at least 70percent, as compared with that of an unexposed control of identicalcomposition and shape.
 27. The molded or extruded thermoplastic articleof claim 16, wherein the retention of tensile strength, on average, isat least 80 percent, as compared with that of an unexposed control ofidentical composition and shape.
 28. The molded or extrudedthermoplastic article of claim 16, wherein the retention of tensilestrength, on average, is at least 90 percent, as compared with that ofan unexposed control of identical composition and shape.
 29. The moldedor extruded thermoplastic article of claim 25, wherein the retention oftensile strength, on average, is at least 70 percent, as compared withthat of an unexposed control of identical composition and shape.
 30. Themolded or extruded thermoplastic article of claim 25, wherein theretention of tensile strength, on average, is at least 80 percent, ascompared with that of an unexposed control of identical composition andshape.